1. Field of the Invention
The present invention relates to an optical code reader for reading a 2-dimensional code affixed to an article and, more particularly, to an optical code reader which is held in a hand of an operator at the time of reading.
2. Description of the Related Art
In many supermarkets, article codes expressed in the form of bar codes are used for sales registration. FIG. 1A shows a bar code which is printed on the label of an article in advance and is read by a bar code scanner in sales registration. The bar code scanner detects an image of the bar code printed on the label of the article, and performs a read processing to obtain an article code from the detected image. This article code is supplied to an electronic cash register via a cable. The electronic cash register then performs a sales registration processing on the basis of the article code supplied from the bar code scanner.
FIG. 2A shows a touch type bar code scanner. In a bar code read operation, an operator holds the bar code scanner in his/her hand, and brings a read window 1A formed on the distal end of the bar code scanner into contact with the label of an article. In this state, the operator depresses a read switch 1B. This scanner has an LED light source and a line CCD inside the read window. These components operate together upon an operation of the read switch 1B. The LED light source illuminates the entire label. The line CCD then receives light reflected by a bar code printed on the label and detects a bar code image corresponding to the light. An LED indicator 1C is turned on when an article code is properly obtained from the bar code image detected by the line CCD, thus informing the operator of the completion of reading a code.
FIG. 2B shows a gun type bar code scanner. In a bar code read operation, an operator holds the bar code scanner in his/her hand, and directs a read window 2A formed on an upper portion of the bar code scanner to the label of an article. In this state, the operator depresses a read switch 2B. This scanner has a laser source and a photo detector inside the read window. These components operate together upon an operation of the read switch 2B. The laser source scans the label in one direction with a laser beam. The photo detector then receives light reflected by a bar code printed on the label and detects a bar code image corresponding to the light.
FIG. 2C shows a stationary type bar code scanner. In a bar code read operation, an operator holds an article in his/her hand, and directs the label of the article to a read window 3A of the bar code scanner fixed in advance. This scanner has a laser source and a photo detector inside the read window 3A. These components operate together all the time. The laser source scans the label in one direction with a laser beam. The line CCD then receives light reflected by a bar code printed on the label and detects a bar code image corresponding to the light.
The above-described bar code is used for article management not only in retail shops such as supermarkets but also in factories, distribution industry, service industry, and the like. With an increase in the number of application fields, article information other than an article code is also expressed in the form of a bar code, and the amount of information is increasing. However, the information capacity of a bar code is relatively small, and hence it is difficult to express a large amount of information in the form of a bar code. In order to overcome such a difficulty, 2-dimensional codes such as the multi-bar code shown in FIG. 1B and the matrix array code shown in FIG. 1C have been developed.
FIG. 3 shows a 2-dimensional code scanner for reading a 2-dimensional code. In this 2-dimensional code scanner, a TV camera 11 photographs a 2-dimensional code printed on a label 14 of an article under room illumination. An image processing unit 12 performs an image processing to obtain article information from an image of the 2-dimensional code photographed by the TV camera 11. A TV monitor 13 then displays the image Of the 2-dimensional code photographed by the TV camera 11.
This 2-dimensional code scanner is expensive, besides being relatively large and heavy. In addition, an operator must direct the label 14 of the article to the TV camera 11 without any inclination, and the focal point and aperture of the TV camera 11 must be adjusted before a read operation. Such a preparation for a read operation will delay start of a 2-dimensional code read operation.
A handy type 2-dimensional code scanner can provide a solution to the above described problem of time consuming preparatory procedures, although such a 2-dimensional code scanner is required to have an enhanced level of adaptability in terms of the size of codes it can read. For instance, it may need to be able to modify the ratio of magnification for reading codes and/or the size of the smallest readable code depending on the size of the cell used for the code to be read.
In a situation where the size of the smallest readable code varies, two 2-dimensional scanners, one that has a relatively small read window as shown in FIG. 4 and hence whose size of the smallest readable code is relatively small and one that has a relatively large read window and shown in FIG. 5 and hence whose size of the smallest readable code is relatively large, may be provided to accommodate the situation but such a 2-dimensional code scanner that can be used only for limited applications cannot easily be modified on the factory floor to adapt it to a different size of the smallest readable code.